The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2003-85778, filed on Mar. 26, 2003, the contents of which is herein expressly incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a battery pack apparatus including a battery pack having a plurality of rechargeable batteries and a cooling medium feeding device for feeding a cooling medium through a cooling medium passage disposed between the rechargeable batteries, and capable of inhibiting temperature variations among the rechargeable batteries.
2. Description of the Related Art
In a battery pack composed of a plurality of rechargeable batteries, the temperature in the rechargeable batteries rises due to heat generation caused by charge and discharge of the batteries, which induces decrease of the battery output, the charge/discharge efficiency, and the battery lifetime. To cope with such problem, it has been conventionally known that a battery pack apparatus is constructed by providing a cooling medium passage between rechargeable batteries and providing a device for feeding a cooling medium through the cooling medium passage (see Japanese Patent Laid-Open Publication No. 2001-167803, for example).
It has been known that, for the purpose of obtaining a desired battery output, as shown in FIG. 4, a battery pack apparatus 31 is constructed by combining a first battery pack 33 composed of a predetermined number of rechargeable batteries 32 and a second battery pack 34 composed of a different number of rechargeable batteries 32 from the first battery pack 33, and serially connecting these battery packs 33 and 34. In the battery pack apparatus thus constructed, there are provided separate cooling medium feeding devices 35 and 36 for the respective battery packs 33 and 34 so that desired combination of battery packs can be provided easily.
It has been also known that, for the purpose of cooling a plurality of battery packs uniformly, the plurality of battery packs are respectively disposed in cooling medium passages, the air exhaust openings of the cooling medium passages being opened to an exhaust collector chamber, and an exhaust duct having a single exhaust fan is connected to the downstream of the exhaust collector chamber so that uniform cooling is achieved by the single exhaust fan (see Japanese Patent Laid-Open Publication No. 2001-102099, for example).
When a plurality of battery packs 33 and 34 are combined to construct a battery pack apparatus 31 as shown in FIG. 4, the construction is made such that the temperature variations among rechargeable batteries 32 in each of the battery packs 33, 34 is restrained within a predetermined range, and the temperature variations in the battery packs 33, 34 will be contained in the ranges of td1 and td2 as shown in FIG. 5. However, since the two battery packs 33 and 34 are different in the number of rechargeable batteries 32, in the feeding characteristic of the cooling medium feeding devices 35 and 36, and in the temperature of the cooling medium, there occurs temperature variation between the battery packs 33 and 34 and the temperature variation in the battery pack apparatus 31 as a whole becomes large as shown by Td in FIG. 5. This will adversely affect the output characteristic and lifetime of the battery pack apparatus 31. It is true that in the respective battery packs 33 and 34 the cooling medium feeding devices 35 and 36 are controlled such that the temperature of the rechargeable batteries 32 will not exceed a predetermined value and thus the final maximum temperatures of the battery packs 33, 34 are restrained at a substantially same level. However, since the temperature history during the change of temperature is different between the two battery packs, the foregoing problem has not been solved.
Also, in the constitution disclosed in Japanese Patent Laid-Open Publication No. 2001-102099, since a single cooling medium feeding device is provided for several battery packs, it is not possible to constitute a battery pack apparatus with a desired battery output simply by combining a plurality of battery packs each composed of an appropriate number of rechargeable batteries. Moreover, if each battery pack is composed of a different number of rechargeable batteries from the other, uniform cooling among the battery packs will be impossible.
The present invention is devised in light of the aforementioned problem of the related art. An object of the present invention is to provide a battery pack apparatus capable of providing a desired battery output by combining a plurality of battery packs and still capable of inhibiting temperature variations among rechargeable batteries.
A battery pack apparatus of the present invention includes: a plurality of battery packs each having a plurality of rechargeable batteries arranged in parallel, with a cooling medium passage interposed therebetween; a plurality of cooling medium feeding devices provided, one for each of the battery packs for feeding a cooling medium through the cooling medium passage in the battery pack; a temperature detector for detecting temperatures of the rechargeable batteries in the respective battery packs; and a controller for controlling the cooling medium feeding devices based on detected temperatures, wherein the controller controls the cooling medium feeding devices such that the maximum or minimum temperatures detected for the respective battery packs substantially match with each other. According to the present invention, the number of rechargeable batteries can be adjusted to obtain a desired battery output, simply by combining a plurality of battery packs each having an appropriate number of rechargeable batteries. Further, temperature variation among the rechargeable batteries is inhibited by controlling the cooling medium feeding devices for the respective battery packs such that the maximum or minimum temperatures of the battery packs substantially match with each other.
Also, a battery pack apparatus according to the invention includes: a plurality of battery packs each having a plurality of rechargeable batteries arranged in parallel, with a cooling medium passage interposed therebetween; a plurality of cooling medium feeding devices provided, one for each of the battery packs for feeding a cooling medium through the cooling medium passage in the battery pack; a temperature detector for detecting temperatures of the rechargeable batteries in each of the battery packs; and a controller for controlling the cooling medium feeding devices based on detected temperatures. In this battery pack apparatus, temperature variation among the rechargeable batteries is inhibited without requiring complicated control operations, by setting the flow characteristic of the cooling medium in the cooling medium feeding devices for the respective battery packs such that when one of the battery packs exhibits the largest temperature distribution range, the temperature distribution ranges of the other battery packs are contained in that largest temperature distribution range.
It is preferable to set the flow resistances of passages for feeding and discharging the cooling medium in the cooling medium feeding devices such that the flow rates of the cooling medium in the cooling medium passages in the respective battery packs are substantially the same as each other.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.